1. Field of the Invention
This invention relates to a process for the manufacture of electrodes for electro-chemical cells such as zinc halogen electric cells and batteries made therefrom, the cathodic electrode being supported in an electrode storage structure formed of a substrate of an anodizable metal or metals of Group IV(A) or Group V(A) of the Periodic Table according to Mendeleef on which has been mounted a layer or layers of porous carbon by a binder of neoprene latex. In such cells the preferred halogen is chlorine and then the electrolyte is zinc chloride.
2. Description of Prior Art
Such an electrode is described in United Kingdom Letters Patent Specification No. 1,258,502 which describes bonding carbon powder with a resin such as nitrile resin latex.
It is known to cure or vulcanize neoprene using a metal oxide such as zinc oxide, the process being based on the bisalkylation theory of neoprene vulcanization as described by Peter Kovacic in "Industrial and Engineering Chemistry" Vol. 47, No. 5, pages 1090-1094 of May 1955. This theory postulates that the cross linking or curing of neoprene takes place at sites on the polymer chain where with chlorine as the halogen, there are tertiary allylic chlorine atoms formed by 1,2 polymerization of chloroprene monomer. This labile chlorine amounts to about 1.5% of the total chlorine in neoprene. The metal oxide, usually zinc oxide, initiates the curing process by reacting with chlorine present to form zinc chloride which is a catalyst for alkylation. Then zinc chloride with bi-functional organic compounds present in the polymer forms cross-links by bisalkylation at the reactive tertiary allylic chlorine sites of nearby polymer chains.
It has been found that by using zinc chloride solution in the mix formulation, in place of say calcium chloride, as proposed in Patent No. 1,258,502 a smooth precipitation of the neoprene latex is achieved. It is known that partial hydrolysis of zinc chloride solution on dilution of the same causes precipitation of zinc oxide or hydroxide. Such dilution occurs during the mixing procedure and therefore produces some zinc oxide to provide a vulcanizing means, and at the same time avoids inclusion of any extraneous impurities in the cured neoprene.
The main object of the present invention is to provide a process for manufacture of zinc halogen cell cathodic electrode support structure having a substrate of an anodizable metal or metals of Group IV(A) or V(A) of the Periodic Table of Mendeleef which has a porous carbon layer bonded thereto by a cured neoprene latex.